The interaction between galloping and Karman-vortex resonance for long rectangular cylinders is a crucial issue in flow-induced vibration. In fact, this type of instability can cause catastrophic oscillations of structures or structural elements exposed to wind but the models for galloping and vortex-induced vibrations fail to predict their onset and the evolution with the flow speed. The main goal of this work is to clarify the most relevant features of the VIV-galloping instability for structures with rectangular cross section and to outline the parameters that control the phenomenon. First, this is pursued through an extensive literature review concerning two- and three-dimensional rectangular prisms with a side ratio in the range 1 to 2, which shows the complexity of the issue and the need for further investigations. Then, the results of new wind tunnel tests in smooth flow on a two-dimensional rectangular 3:2 cylinder were provided. This cross section was found very prone to instability and large-amplitude vibrations were observed also for high values of the Scruton number (non-dimensional product of mass and damping) and relatively low wind speeds. Also, for low Scruton numbers the paper underscores the possibility to observe non-negligible excitation at low wind speed due to secondary vortex-resonance. Finally, the non-conservativeness of the values provided by Eurocode 1 for the galloping stability parameter and Strouhal number is discussed.
VIV–galloping instability of rectangular cylinders: Review and new experiments / Claudio Mannini; Antonino Maria Marra; Gianni Bartoli. - In: JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS. - ISSN 0167-6105. - STAMPA. - 132:(2014), pp. 109-124. [10.1016/j.jweia.2014.06.021]
VIV–galloping instability of rectangular cylinders: Review and new experiments
MANNINI, CLAUDIO;MARRA, ANTONINO MARIA;BARTOLI, GIANNI
2014
Abstract
The interaction between galloping and Karman-vortex resonance for long rectangular cylinders is a crucial issue in flow-induced vibration. In fact, this type of instability can cause catastrophic oscillations of structures or structural elements exposed to wind but the models for galloping and vortex-induced vibrations fail to predict their onset and the evolution with the flow speed. The main goal of this work is to clarify the most relevant features of the VIV-galloping instability for structures with rectangular cross section and to outline the parameters that control the phenomenon. First, this is pursued through an extensive literature review concerning two- and three-dimensional rectangular prisms with a side ratio in the range 1 to 2, which shows the complexity of the issue and the need for further investigations. Then, the results of new wind tunnel tests in smooth flow on a two-dimensional rectangular 3:2 cylinder were provided. This cross section was found very prone to instability and large-amplitude vibrations were observed also for high values of the Scruton number (non-dimensional product of mass and damping) and relatively low wind speeds. Also, for low Scruton numbers the paper underscores the possibility to observe non-negligible excitation at low wind speed due to secondary vortex-resonance. Finally, the non-conservativeness of the values provided by Eurocode 1 for the galloping stability parameter and Strouhal number is discussed.File | Dimensione | Formato | |
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